The coating of substrate bodies of hard metal, cermets, ceramics or steel with hard-facing and wear-reducing layers of hard materials, mixtures of hard materials or ceramics, is known in the production of cutting tools. The coatings can be carbides, nitrides, carbonitrides, oxycarbonitrides, oxides and/or borides of an element from Groups IVa to Via of the Periodic Table. Examples of such wear-reducing materials include TiC, TiN, Ti(C,N) and ceramics like Al.sub.2 O.sub.3 and ZrO.sub.2. At high cutting speeds and/or large cutting cross sections, the high temperatures at the tool/workpiece interface give rise to enhanced wear, especially with workpieces which are difficult to machine, and ultimately to breakage of the tool. To minimize the temperatures which develop in machining of such workpieces, i.e. at the chip-forming region, coolants and lubricants can be used which are environmentally unsound and can produce noxious and toxic waste and which are costly because of the cost of the coolant and/or lubricant.
It is known to provide solid dry lubricant films, for example of molybdenum disulfide (DE-A 24 15 25)and to improve the adhesion of such layers to the substrate by first sputtering the base layer of MoS.sub.2 or WS.sub.2 onto the substrate with a thickness of 1 to 2 .mu.m a and then applying the dry lubricant film of MOS.sub.2 or WS2.
In DD 202 898 it has been proposed to sputter layers of molybdenum disulfide or the like on tools used for chip removal machining, punching, drawing or like shaping, the layer thickness being in the nm range. In these systems, a substrate body is provided with a hard layer by sputtering of a coating which has a hexagonal lattice structure. EP 0 534 905 A2 proposes a plasma vapor deposition (PVD) coating of chip removing tools with, for example molybdenum disulfide.
The cathodic sputtering of molybdenum disulfide layers on a substrate body or on hard material coating previously applied to the substrate body can provide MOS.sub.2 crystallites with an unsatisfactory orientation. To keep the friction coefficient of such a layer as small as possible, the hexagonal lattice component of the MOS.sub.2 layer should be so oriented that the hexagonal planes run parallel to the surface and the axes of the hexagonal lattice structures run perpendicular or normal to the surface. This has been found to improve the oxygen resistance of the layer.
DE 35 16 933 A1 proposes that the ratio of the water vapor partial pressure for such coating be less than 10.sup.-7 millibar/1.6 mgm.sup.-2 s.sup.-1 which can be attained in high cost.
Apart from the fact that the PVD process requires pure gas atmospheres, i.e. gas atmospheres free from foreign substances, a drawback of the PVD process is that a directed particle stream must pass from the target source to the substrate, thereby requiring that the substrate be rotated about three axes for uniform coating.